Slot drains are one of the most practical means of providing a large capacity carrier drain integral within a section of minimal footprint. Offering the same durability characteristics for which slipform formations are renowned, the system is a popular choice for the centre reserve adjacent to the concrete median barrier where space is obviously at a premium. Other situations where the concept proves popular are highways where there is little longitudinal fall. Working principal of the slot drain as its name suggests sees surface water accessing the drain through a linear slot. This provides an unimpeded access to the large capacity carrier drain within the structure. To achieve the unique formation of the slot drain, the mould fitted to the kerbing machine is complimented by an inflated void former. This is placed along the route of the slot drain in advance of formation and inflated through its connection to an air line from an accompanying compressor.A further manifestation of the experience necessary for successful completion of the process, the air pressure must be to a precise level.